1. Field of the Invention
The present invention relates to an automatic document feeder, especially to an automatic document feeder with double-side scanning function.
2. The Related Art
In order to increase the efficiency of scanning and to achieve the function of double-side scanning, most scanners are equipped with an automatic document feeder.
Referring to FIG. 1, a sectional view of a conventional automatic document feeder is shown. The automatic document feeder defines a paper transmitting path for transmitting documents, and the paper transmitting path includes an input tray 11′, an input path 12′, a scanning section 13′, an output path 14′ and an output tray 15′. A reverse path 16′ is connected between the input path 12′ and the output path 14′.
In order to transmit documents through respective path above, a plurality of transmitting devices are disposed along corresponding path. For example, a pickup device 20′ is disposed at the entrance of the input path 12′, scan roller 171′, transmitting roller 172′ are disposed along the input path 12′ and the output path 14′, and an output device 30′ is disposed at the exit of the output path 14′.
Various transmitting devices act in different ways. In detail, the pickup device 20′ will press downward to documents in the input tray 11′ to pick one of the documents into the input path 12′ when the scanning process starts, and rise up to avoid multi-feed when the picked document enters the input path 12′ and reaches the scan roller 171′. The scan rollers 171′ and the transmitting roller 172′ will keep rotating in a same direction to transmit un-scanned documents for scanning and to discharge scanned documents to the output tray 15′ in the whole scanning process. The output device 30′ includes an acting roller 31′ and a movable pressure roller 32′. The pressure roller 32′ keeps contact with the acting roller 31′ to transmit documents in single-side scanning process, but in the double-side scanning process, the output device 30′ will reverse and transmit the document back to the reverse path 16′ when the document passes through the scanning section 13′. Furthermore, when the document passes through the reverse path 16′ and is transmitted to the output device 30′ again, the pressure roller 32′ will swing downward and separate from the acting roller 31′ to avoid the document being jammed at the output device 30′.
As described above, the scan rollers 171′ and the transmitting roller 172′ basically rotate in the same direction, the pickup device 20′ and the output device 30′ can change the rotate directions according to the position of the document, and the pressure roller 32′ of the output device 30′ is movable to contact with the acting roller 31′ or to separate from the acting roller 31′, so as to make the automatic document feeder achieve double-side scanning for the document. However, the conventional automatic document feeder has a complex structure and is difficult to be miniaturized. Therefore, it is necessary to improve the conventional automatic document feeder.